Stingray movement could inspire the next generation of submarines

Submitted

Richard Bottom, left, and Iman Borazjani hope their research on how stingrays swim will lead to the design of new underwater vehicles. (photo by Douglas Levere)

The
fish's unique way of swimming could improve deep-sea vehicles' agility and fuel
efficiency

by Marcene
Robinson

University at Buffalo

Stingrays swim through water with such ease that
researchers from the University at Buffalo and Harvard University are studying
how their movements could be used to design more agile and fuel-efficient
unmanned underwater vehicles.

The vehicles could allow researchers to more efficiently
study the mostly unexplored ocean depths, and they could also serve during
cleanup or rescue efforts.

"Most fish wag their tails to swim. A stingray's
swimming is much more unique, like a flag in the wind," said Richard Bottom, a
UB mechanical engineering graduate student participating in the research.

Bottom and Iman Borazjani, UB assistant professor of
mechanical and aerospace engineering, set out to investigate the form-function
relationship of the stingray - why it looks the way it does and what it gets
from moving the way it does.

They will explain their findings at the 66th Annual
Meeting of the American Physical Society Division of Fluid Dynamics. Their
lecture, "Biofluids: Locomotion III - Flying," is at 4:45 p.m. Sunday, Nov. 24,
in Pittsburgh.

The researchers used computational fluid dynamics,
which employs algorithms to solve problems that involve fluid flows, to map the
flow of water and the vortices around live stingrays.

The study is believed to be the first time the
leading-edge vortex, the vortex at the front of an object in motion, has been
studied in underwater locomotion, Borazjani said. The leading-edge vortex has
been observed in the flight of birds and insects, and is one of the most
important thrust enhancement mechanics in insect flight.

The vortices on the waves of the stingrays' bodies cause
favorable pressure fields - low pressure on the front and high pressure on the
back - which push the ray forward. Because movement through air and water are
similar, understanding vortices are critical.

"By looking at nature, we can learn from it and come
up with new designs for cars, planes and submarines," Borazjani said. "But
we're not just mimicking nature. We want to understand the underlying physics
for future use in engineering or central designs."

Studies have already proven that stingray motion
closely resembles the most optimal swimming gait, Bottom said. Much of this is
due to the stingray's unique flat and round shape, which allows them to easily
glide through water.

Borazjani and Bottom plan to continue their research
and study the differences in movement among several types of rays.